Mitral heart valve replacement

ABSTRACT

A prosthetic heart valve having an inflow end, an outflow end and a longitudinal axis extending from the inflow end to the outflow end includes a collapsible and expandable stent including a plurality of cells arranged in at least one row extending around a circumference of the stent. The stent further includes at least one engaging arm joined to one of the cells adjacent the outflow end and having a free end extending toward the inflow end, the engaging arm being movable between a loaded condition in which the engaging arm is oriented substantially parallel with the longitudinal axis of the stent, a partially-released condition in which the engaging arm forms a first angle with the longitudinal axis of the stent, and a fully-released condition in which the engaging arm forms a second angle with the longitudinal axis of the stent, the first angle being larger than the second angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application No. 62/335,294 filed May 12, 2016, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present disclosure relates to heart valve replacement and, inparticular, to collapsible prosthetic heart valves. More particularly,the present disclosure relates to devices and methods for replacing thefunctionality of a native mitral valve.

Diseased and/or defective heart valves may lead to serious healthcomplications. One method of addressing this condition is to replace anon-functioning heart valve with a prosthetic valve. Prosthetic heartvalves that are collapsible to a relatively small circumferential sizecan be delivered into a patient less invasively than valves that are notcollapsible. For example, a collapsible valve may be delivered into apatient via a tube-like delivery apparatus such as a catheter, a trocar,a laparoscopic instrument, or the like. This collapsibility can avoidthe need for a more invasive procedure such as full open-chest,open-heart surgery.

Collapsible prosthetic heart valves typically take the form of a valvestructure mounted on a stent. There are two types of stents on which thevalve structures are ordinarily mounted: a self-expanding stent and aballoon-expandable stent. To place such valves into a delivery apparatusand ultimately into a patient, the valve must first be collapsed orcrimped to reduce its circumferential size.

When a collapsed prosthetic valve has reached the desired implant sitein the patient (e.g., at or near the annulus of the patient's heartvalve that is to be replaced by the prosthetic valve), the prostheticvalve can be deployed or released from the delivery apparatus andre-expanded to full operating size. For balloon-expandable valves, thisgenerally involves releasing the entire valve, assuring its properlocation, and then expanding a balloon positioned within the valvestent. For self-expanding valves, on the other hand, the stentautomatically expands as the sheath covering the valve is withdrawn.

SUMMARY OF THE INVENTION

In some embodiments, a prosthetic heart valve has an inflow end, anoutflow end and a longitudinal axis extending from the inflow end to theoutflow end and includes a collapsible and expandable stent including aplurality of cells arranged in at least one row extending around acircumference of the stent. The stent further includes at least oneengaging arm joined to one of the cells adjacent the outflow end andhaving a free end extending toward the inflow end, the engaging armbeing movable between a loaded condition in which the engaging arm isoriented substantially parallel with the longitudinal axis of the stent,a partially-released condition in which the engaging arm forms a firstangle with the longitudinal axis of the stent, and a fully-releasedcondition in which the engaging arm forms a second angle with thelongitudinal axis of the stent, the first angle being larger than thesecond angle. A collapsible and expandable valve assembly is disposedwithin the stent and having a plurality of leaflets.

In some embodiments, a prosthetic heart valve has an inflow end and anoutflow end, and may include a collapsible and expandable stentincluding a plurality of cells arranged in at least one row extendingaround a circumference of the stent. The stent further includes at leastone engaging arm joined to one of the cells adjacent the outflow end andhaving a free end extending toward the inflow end, the engaging armbeing connected to a selected cell, the one cell having two upper strutsjoined to one another at an upper apex, two lower struts joined oneanother at a lower apex, the lower struts being joined to the upperstruts at corners, the engaging arm being joined to the lower struts ofthe one cell and movable between a loaded condition and a relaxedcondition, the engaging arm being sloped with respect to a longitudinalaxis of the one cell in the relaxed condition. A collapsible andexpandable valve assembly may be disposed within the stent and having aplurality of leaflets.

In some embodiments, a method of delivering a prosthetic heart valve mayinclude providing a collapsible and expandable valve assembly and acollapsible and expandable stent having an inflow end, an outflow end,and a longitudinal axis extending from the inflow end to the outflowend, the stent including a plurality of cells arranged in at least onerow, each row extending around a circumference of the stent, the stentfurther including at least one engaging arm joined to one of the cellsadjacent the outflow end and having a free end extending toward theinflow end, the one cell having two upper struts joined to one anotherat an upper apex, two lower struts joined one another at a lower apex,the lower struts being joined to the upper struts at corners, theengaging arm being joined to the lower struts of the one cell. The stentand valve assembly may be loaded within a delivery sheath, and thedelivery sheath may be advanced to a patient's native valve annulus.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are disclosed herein withreference to the drawings, wherein:

FIG. 1 is a schematic representation of a human heart showing atransapical delivery approach;

FIG. 2A is a schematic representation of a native mitral valve andassociated structures during normal operation;

FIG. 2B is a schematic representation of a native mitral valve having aprolapsed leaflet;

FIG. 3 is a schematic longitudinal cross-section of one embodiment of aprosthetic heart valve having a stent, a valve assembly, and a frame;

FIG. 4 is a schematic longitudinal cross-section of one embodiment of aprosthetic heart valve having a stent, a valve assembly, and a flaredportion;

FIG. 5A is a developed view of one example of a stent having a flaredportion and a plurality of engaging arms;

FIG. 5B is a developed view of another example of a stent having aflared portion and a plurality of engaging arms;

FIGS. 6A and 6B are highly schematic developed views of one example of acuff configured for coupling to the stent of FIG. 5A;

FIGS. 7A and 7B are highly schematic developed views of another exampleof a cuff configured for coupling to the stent of FIG. 5A;

FIG. 8A is a highly schematic top view of a skirt for a prosthetic heartvalve;

FIG. 8B is a top perspective view of a prosthetic heart valve stenthaving the skirt of FIG. 8A;

FIG. 8C is a bottom perspective view of a prosthetic heart valve stenthaving the skirt of FIG. 8B;

FIGS. 9A-C are highly schematic top views of several variants of a skirtfor a prosthetic heart valve;

FIG. 10 is a highly schematic top view of another example of a skirthaving multiple slits for reduced puckering at the seams;

FIG. 11 is a highly schematic developed view of one example of a cuffand a skirt for coupling to a stent having a flared portion and aplurality of engaging arms;

FIGS. 12A-C are photographs showing the side, top and bottom,respectively, of a fully assembled prosthetic heart valve;

FIG. 13 is a developed view of one example of a stent having multiplehorseshoes to aid in suturing;

FIGS. 14A and 14B are developed views showing portions of a stent havingengaging arms of different shapes;

FIG. 15 is a developed view of one example of a stent having circularsupports for accepting radiopaque markers;

FIGS. 16A-B are a photograph and a schematic representation of theprofile of a variation of a prosthetic heart valve having a braidedcrown;

FIGS. 16C-E are a photograph and schematic representations of theprofile of a variation of a prosthetic heart valve having anotherexample of a braided crown;

FIGS. 17A-G are photographs and schematic representations a variation ofa stent having teeter-totter engaging arms; and

FIGS. 18A-C are photographs and schematic representations of a variationof a stent having criss-crossing engaging arms.

Various embodiments of the present disclosure will now be described withreference to the appended drawings. It is to be appreciated that thesedrawings depict only some embodiments of the disclosure and aretherefore not to be considered limiting of its scope.

DETAILED DESCRIPTION

In conventional collapsible prosthetic heart valves, the stent isusually anchored within the native valve annulus via radial forcesexerted by the expanding stent against the native valve annulus. If theradial force is too high, damage may occur to heart tissue. If, instead,the radial force is too low, the heart valve may move from its implantedposition, for example, into the left ventricle. Because such anchoringpartly depends on the presence of calcification or plaque in the nativevalve annulus, it may be difficult to properly anchor the valve inlocations where plaque is lacking (e.g., the mitral valve annulus).Additionally, in certain situations it may be preferable to restorenative valve leaflet function rather than implanting a prosthetic deviceto replace that function.

In view of the foregoing, there is a need for further improvements tothe devices, systems, and methods for replacing the function of a nativeheart valve, such as a mitral valve, a tricuspid valve, an aortic valve,or a pulmonary valve. Among other advantages, the present disclosure mayaddress one or more of these needs. While many of the examples aredescribed herein with reference to a specific valve (e.g., a mitralvalve or a tricuspid valve), it will be understood that many of theseexamples are not so limited and that the concepts described applyequally to other heart valves unless expressly limited herein.

Blood flows through the mitral valve from the left atrium to the leftventricle. As used herein, the term “inflow,” when used in connectionwith a prosthetic mitral heart valve, refers to the end of the heartvalve closest to the left atrium when the heart valve is implanted in apatient, whereas the term “outflow,” when used in connection with aprosthetic mitral heart valve, refers to the end of the heart valveclosest to the left ventricle when the heart valve is implanted in apatient. When used in connection with a prosthetic aortic valve,“inflow” refers to the end closest to the left ventricle and “outflow”refers to the end closest to the aorta. The same convention isapplicable for other valves wherein “inflow” and “outflow” are definedby the direction of blood flow therethrough. Also, as used herein, thewords “substantially,” “approximately,” “generally” and “about” areintended to mean that slight variations from absolute are includedwithin the scope of the structure or process recited.

FIG. 1 is a schematic representation of a human heart 100. The humanheart includes two atria and two ventricles: a right atrium 112 and aleft atrium 122, and a right ventricle 114 and a left ventricle 124. Asillustrated in FIG. 1, the heart 100 further includes an aorta 110, andan aortic arch 120. Disposed between the left atrium and the leftventricle is the mitral valve 130. The mitral valve 130, also known asthe bicuspid valve or left atrioventricular valve, is a dual-flap thatopens as a result of increased pressure in the left atrium as it fillswith blood. As atrial pressure increases above that of the leftventricle, the mitral valve opens and blood passes toward the leftventricle. Blood flows through heart 100 in the direction shown byarrows “B”.

A dashed arrow, labeled “TA”, indicates a transapical approach forrepairing or replacing heart valves, such as a mitral valve. Intransapical delivery, a small incision is made between the ribs and intothe apex of the left ventricle 124 at position “P1” in heart wall 150 todeliver a prosthesis or device to the target site.

FIG. 2A is a more detailed schematic representation of a native mitralvalve 130 and its associated structures. Mitral valve 130 includes twoflaps or leaflets, a posterior leaflet 136 and an anterior leaflet 138,disposed between left atrium 122 and left ventricle 124. Cord-liketendons known as chordae tendineae 134 connect the two leaflets 136, 138to the medial and lateral papillary muscles 132. During atrial systole,blood flows from the left atrium to the left ventricle down the pressuregradient. When the left ventricle contracts in ventricular systole, theincreased blood pressure in the chamber pushes the mitral valve toclose, preventing backflow of blood into the left atrium. Since theblood pressure in the left atrium is much lower than that in the leftventricle, the flaps attempt to evert to the low pressure regions. Thechordae tendineae prevent the eversion by becoming tense, thus pullingthe flaps and holding them in the closed position.

FIG. 2B is a schematic representation of a prolapsed mitral valve.Posterior leaflet 136 has prolapsed into left atrium 122. Moreover,certain chordae tendineae have stretched and others have ruptured.Because of damaged chordae 134 a, even if posterior leaflet 136 returnsto its intended position, it will eventually resume the prolapsedposition due to being inadequately secured. Thus, mitral valve 130 isincapable of functioning properly and blood is allowed to return to theleft atrium and the lungs. It will be understood that, in addition tochordae damage, other abnormalities or failures may be responsible formitral valve insufficiency.

FIG. 3 is a longitudinal cross-section of prosthetic heart valve 200 inaccordance with one embodiment of the present disclosure. Prostheticheart valve 200 is a collapsible prosthetic heart valve designed toreplace the function of the native mitral valve of a patient (see nativemitral valve 130 of FIGS. 1-2). Generally, prosthetic valve 200 hasinflow end 210 and outflow end 212. Prosthetic valve 200 may besubstantially cylindrically shaped and may include features foranchoring, as will be discussed in more detail below. When used toreplace native mitral valve 130, prosthetic valve 200 may have a lowprofile so as not to interfere with atrial function.

Prosthetic heart valve 200 includes stent 250, which may be formed frombiocompatible materials that are capable of self-expansion, such as, forexample, shape memory alloys including Nitinol. Alternatively, stent 250may be formed of a material suitable for balloon-expansion. In oneexample, stent 250 is formed by laser cutting a predetermined patterninto a metallic tube. Stent 250 may include a plurality of struts 252that form cells 254 connected to one another in one or more annular rowsaround the stent. Cells 254 may all be of substantially the same sizearound the perimeter and along the length of stent 250. Alternatively,cells 254 near inflow end 210 may be larger than the cells near outflowend 212. Stent 250 may be expandable to provide a radial force to assistwith positioning and stabilizing prosthetic heart valve 200 within thenative mitral valve annulus.

Prosthetic heart valve 200 may also include valve assembly 260,including a pair of leaflets 262 attached to a cylindrical cuff 264.Leaflets 262 replace the function of native mitral valve leaflets 136and 138 described above with reference to FIG. 2. That is, leaflets 262coapt with one another to function as a one-way valve. It will beappreciated, however, that prosthetic heart valve 200 may have more thantwo leaflets when used to replace a mitral valve or other cardiac valveswithin a patient. Valve assembly 260 of prosthetic heart valve 200 maybe substantially cylindrical, or may taper outwardly from outflow end212 to inflow end 210. Both cuff 264 and leaflets 262 may be wholly orpartly formed of any suitable biological material, such as bovine orporcine pericardium, or polymers, such as PTFE, urethanes and the like.

When used to replace a native mitral valve, valve assembly 260 may besized in the range of about 20 mm to about 40 mm in diameter. Valveassembly 260 may be secured to stent 250 by suturing to struts 252 or byusing tissue glue, ultrasonic welding or other suitable methods.

An optional frame 300 may surround and house valve assembly 260 andstent 250. Frame 300 may be formed of a braided material in variousconfigurations to create shapes and/or geometries for engaging tissueand filling the spaces between valve assembly 260 and the native valveannulus. As shown in FIG. 3, frame 300 includes a plurality of braidedstrands or wires 305 arranged in three-dimensional shapes. In oneexample, wires 305 form a braided metal fabric that is both resilientand capable of heat treatment substantially to a desired preset shape.One class of materials which meets these qualifications is shape memoryalloys. One example of a suitable shape memory alloy is Nitinol. It isalso contemplated that wires 305 may comprise various materials otherthan Nitinol that have elastic and/or memory properties, such as springstainless steel, alloys such as Elgiloy®, Hastelloy®, and MP35N®, CoCrNialloys (e.g., trade name Phynox), CoCrMo alloys, or a mixture of metaland polymer fibers. Depending on the individual material selected, thestrand diameter, number of strands, and pitch may be altered to achievedesired properties for frame 300.

In the simplest configuration of frame 300, shown in FIG. 3, frame 300may be formed in a cylindrical or tubular configuration having inlet end310, outlet end 312 and lumen 315 extending between inlet end 310 andoutlet end 312 for housing stent 250 and valve assembly 260. However, incertain embodiments stent 250 may be omitted, and valve assembly 260 maybe directly attached to frame 300 using any of the techniques describedabove for attaching valve assembly 260 to stent 250. Frame 300 may beradially collapsed from a relaxed or preset configuration to acompressed or reduced configuration for delivery into the patient. Oncereleased after delivery, the shape-memory properties of frame 300 maycause it to re-expand to its relaxed or preset configuration. Frame 300may also be locally compliant in a radial direction such that a forceexerted in the direction of arrow F deforms a portion of the frame. Inthis manner, irregularities in the native valve annulus may be filled byframe 300, thereby preventing paravalvular leakage. Moreover, portionsof frame 300 may endothelialize and in-grow into the heart wall overtime, providing permanent stability and a low thrombus surface.

FIG. 4 illustrates one variation in which prosthetic heart valve 400includes additional features to aid in fixing the valve at apredetermined location within the native valve annulus. Prosthetic heartvalve 400 generally extends between inflow end 410 and outflow end 412and includes all of the elements disclosed above including stent 250formed of struts 252, and valve assembly 260 having leaflets 262 andcuff 264. Stent 250 may be substantially cylindrical and may furtherinclude flared portion 450 adjacent inflow end 410 that projectsradially outward from the cylindrical stent to anchor the stent at apredetermined location in the native valve annulus. Flared portion 450forms an angle α with the longitudinal axis of stent 250. In someexamples, angle α may be between about 80 degrees and about 180 degrees.In some examples, angle α may be between about 90 and 110 degrees.Moreover, as shown in FIG. 4, flared portion 450 may be curved. Thus,flared portion 450 may have an initial takeoff angle α and then roundout along its length to form a second angle β with the longitudinal axisof stent 250 near its distal end. As a result of the rounding, secondangle β may be between about 160 degrees and about 180 degrees. Duringdelivery, flared portion 450 may be compressed against the outside ofcollapsed stent 250 within a sheath of a delivery device and may returnto its flared configuration when released from the sheath. Whenprosthetic heart valve 400 is used to replace the function of a nativemitral valve, flared portion 450 may be disposed at least partiallywithin the left atrium. Details of flared portion 450 are exploredfurther below with reference to FIGS. 5A and 5B.

FIG. 5A is a developed view of a stent 500A suitable for use in a mitralheart valve prosthesis. Stent 500A generally extends in a lengthdirection between inflow end 502 and outflow end 504 and includes aplurality of struts 506 forming rows of cells 510A, 520A, 530A, and aplurality of commissure features 508. First row of cells 510A isdisposed adjacent outflow end 504 and includes symmetric cells 512,typically disposed adjacent commissure features 508, and asymmetriccells 514 at selected positions within first row 510A. Symmetric cells512 may be substantially diamond-shaped and include four substantiallystraight struts 506 a-d of substantially equal length. Asymmetric cells514 may include a pair of substantially straight struts 515 a,515 bwhich form a V-shape attached to substantially curved struts 516 a,516b. Nested within selected ones of asymmetric cells 514 are engaging arms518, which extend generally from the connection of one cell 514 to theadjacent cells on either side thereof in row 510A. Engaging arms 518have a curved shape which generally follows the curved shape of struts516 a, 516 b, and may be configured to engage portions of heart tissue(e.g., native valve leaflets) by contacting, clasping, gripping, orsecuring to the tissue or otherwise preventing, minimizing or limitingthe movement of stent 500A when the stent is deployed in a patient aspart of a prosthetic heart valve. Second row of cells 520A may include aplurality of cells 522 formed by two struts shared with cells from firstrow 510A (e.g., struts 506 c, 506 d, 516 a, 516 b) and two substantiallystraight struts 526 a, 526 b. A third row of cells 530A includesenlarged cells 532 formed of struts 536 a-d, each of which is longerthan struts 506 a-d. Third row 530A may include cells that have a lengthL1 that is greater than the lengths of other cells. In at least someexamples, length L1 may be between about 20 mm and about 30 mm. Thirdrow 530A of enlarged cells 532 may be configured to form a diametergreater than the diameter formed by the first two rows. Thus, as shownin the cross-sectional schematic of FIG. 4, when stent 500A fullyexpands, third row 530A of enlarged cells 532 forms a flared portion.Optionally, a number of retainers 540 may be disposed on selectedenlarged cells 532 as well as on commissure features 508 to help holdstent 500A in the delivery apparatus and aid in its deployment.

As shown in FIG. 5A, stent 500A is formed of three rows of cells, eachrow having nine cells and is thus referred to as a nine-cellconfiguration. As briefly discussed, engaging arms 518 are nested withinselected asymmetric cells 514 to engage the native valve leaflets.Because the native mitral valve includes two native leaflets, theillustrated example includes two engaging arms 518 for mating with eachnative valve leaflet, the first pair of engaging arms being spaced apartfrom the second pair of engaging arms so that they are approximatelycontralateral to one another. It will be understood, however, that in anine-cell stent configuration, it may be difficult to provide pairs ofengaging arms that are exactly 180 degrees apart from one another.

FIG. 5B shows a variation in which stent 500B has a twelve-cellconfiguration (i.e., each row of cells in stent 500B includes twelvecells). Stent 500B extends between inflow end 502 and outflow end 504and includes a first row of cells 510B having symmetric cells 512 andasymmetric cells 514, a second row of cells 520B having cells 522 and athird row of cells 530B having enlarged cells 532. Engaging arms 518 arenested within two pairs of asymmetric cells 514 a, 514 b and 514 c, 514d, each pair of asymmetric cells being spaced from one another by asymmetric cell. In this example, pairs of engaging arms 518 are offsetfrom one another as much as possible, and provide a generally moresymmetric configuration than stent 500A, which allows for simplercoupling of the leaflets. Thus, the positioning of the engaging arms maybe affected by the number of cells in the rows of a stent.

As shown in FIGS. 6A and 6B, a cuff 600 may be disposed over a portionof stent 500A. As illustrated, cuff 600 includes three separate segments610 a-c that are disposed over portions of the first and second rows ofcells 510A, 520A and joined together at seams 612. By using a cuffformed of three segments, greater flexibility is provided for makingfiner adjustments to facilitate the assembly process. FIG. 6Billustrates cuff segment 610 a in greater detail, cuff segments 610B and610 c being substantially the same. As shown, cuff segment 610 aincludes a first portion 620 sized to be disposed over commissurefeature 508, a second portion 622 for covering symmetric cell 512 offirst row 510A, and three substantially equal third portions 624,626,628for covering three cells 522 of second row 520A. It will be understoodthat cuff 600 may be disposed on either the luminal or the abluminalsurface of stent 500A and that the shape of the cuff may be modified asneeded for a stent having a twelve-cell configuration. Additionally, aunitary cuff may be used instead of the three-segmented example shown.When disposed on the abluminal surface of stent 500A, cuff segment 610 amay be configured to allow engaging arms 518 to extend therethrough toreach and couple to the native valve leaflets. Thus, engaging arms 518are preferably unobstructed by cuff 600.

In another variation shown in FIGS. 7A and 7B, cuff 700 may be disposedover a portion of stent 500A. As illustrated, cuff 700 includes threeseparate segments 710 a-c that are disposed over portions of the firstand second rows 510A,520A and joined together at seams 712. Thedifferences between cuff 700 and cuff 600 described above are morereadily identifiable by looking at the detailed view of FIG. 7B. Asshown, cuff segment 710 a includes a first portion 720 sized to bedisposed over commissure feature 508. Second portion 722 coverssymmetric cell 512 of first row 510A and includes two additionalsections 723 for covering asymmetric cells 514. A third portion 724covers cells 522 of second row 520A and has a substantially straightedge 750 that runs horizontally across the lower corners of cells 532.Cuff 700 is shaped to allow engaging arms 518 to extend over the cuffand couple to the native valve leaflets. Cuff segments 710 b and 710 cmay have the same configuration as cuff segment 710 a.

In addition to the cuff, a skirt may be disposed over the third row ofcells 530A,530B to cover flared portion 450 of the stent. FIG. 8illustrates one example of a skirt 800A configured to cover the thirdrow of cells in a twelve-cell stent configuration (e.g., stent 500B ofFIG. 5B). For the sake of clarity, skirt 800A will be described ashaving multiple portions or components. It will be understood, however,that the skirt may be formed of a single piece of tissue, fabric orpolymeric material cut into a predetermined shape and that the portionsor components described herein are only indicated for the sake ofdescription and may not be readily discernible from the whole.

As shown, skirt 800A generally includes a hub 802 having a number ofsides 803. Hub 802 is shown in the shape of a dodecagon in order tocomplement a twelve-celled stent. A circular cutout 804 is formed in thecenter of hub 802 to form void 806 for accepting a portion of the stent.In at least some examples, cutout 804 is formed with a circumferenceapproximately equal to the circumference of a fully expanded stent atthe second row of cells. A plurality of quadrilateral tabs 810 extendfrom the sides of hub 802. In the case of a dodecagon hub, twelvequadrilateral tabs 810 are formed around the perimeter of the hub, oneextending from each side 803 of hub 802.

Due to the desired increasing diameter of flared portion 450 of thestent, triangular slits 812 are provided between quadrilateral tabs 810.However, when fully assembled to the stent, edges 811 a,811 b ofadjacent quadrilateral tabs 810 a, 810 b will be sewn or otherwisecoupled together to close slits 812. Quadrilateral tabs 810 are coupledto one another at seams 830 to form a continuous surface. It will beunderstood that quadrilateral tabs 810 may be formed such that seams 830align with struts of stent 500A as shown.

Instead of being formed as a single piece of material, a skirt may beformed in multiple segments. As seen in FIGS. 9A-B, skirt 900 is formedof three equal segments 901A-C. Each of segments 901A-C may include anumber of quadrilateral tabs 910 a-d extending from a hub portion 902A.It will be understood that each of segments 901A-C may be formed to besubstantially the same size and may include the same number ofquadrilateral tabs. An optional coupling 930 may be added to each ofsegments 910A-C and configured to overlap with the hub portion of anadjacent segment to add integrity to the assembly. It will be understoodthat variations are possible by changing the size and/or shape of thesegments. In some variations, the number of quadrilateral tabs may beincreased or decreased as desired. For example, as shown in FIG. 9C, askirt may be formed of three segments 901D, each segment having threequadrilateral tabs 910 e-910 g.

In another variation, shown in FIG. 10, skirt 1000 includes more slitsto reduce puckering at the seams. Similar to skirt 800A, skirt 1000includes a hub 1002 having circular cutout 1004 at its center to formvoid 1006 for accepting a portion of the stent. Extending from hub 1002and disposed on its perimeter are a series of alternating wedgesincluding first wedges 1010 and second wedges 1020. In the examplesshown, first wedges 1010 are substantially triangular and are attachedat an edge of the triangle to hub 1002, and second wedges 1020 aresubstantially concave quadrilaterals and are attached to hub 1002 at apoint of the triangle. Collectively, wedges 1010 and 1020 define aseries of triangles that alternate in their connection to hub 1002. Eachfirst wedge 1010 is disposed between adjacent second wedges 1020 andspaced from the second wedges by slits 1030 a, 1030 b. When fullyassembled, first and second wedges 1010, 1020 adjoin one another attheir edges to provide a continuous layer over a row of cells forming aflared portion 450. It will be understood, however, that the shapes offirst and second wedges 1010, 1020 may be varied from the shapes shownand described herein and that skirt 1000 may, for example, include aseries of wedges in the shape of triangles instead of concavequadrilaterals that are arranged so that each triangle is inverted withrespect to an adjacent triangle.

FIG. 11 illustrates one possible suture pattern for attaching a skirt,such as skirt 800A, to stent 500A having cuff 600. A first suturepattern 51 may be formed across the tops of cells 532 in third row ofcells 530A at inflow end 502 of stent 500A, and around the circumferenceof the stent to attach skirt 800A to the stent. A second suture patternS2 may be formed parallel to the first suture pattern 51 and across theends of cells 512, 514 in first row of cells 510A and throughapproximately the midline of cells 522 in second row of cells 520A. Athird suture pattern S3 may consist of a zigzag pattern along the strutsforming the upper half of enlarged cells 532 of third row of cells 530A,and a fourth suture pattern S4 may form a second zigzag pattern alongthe struts forming the lower half of enlarged cells 532, the fourthsuture pattern S4 being a mirror image of the third suture pattern S3.

A fully assembled prosthetic heart valve 1200 is shown in FIG. 12A andincludes stent 500A having inflow end 502 and outflow end 504. Inflowand outflow end views of prosthetic heart valve 1200 are shown in FIGS.12B and 12C, respectively. Cuff 600 is disposed on the abluminal surfaceof a portion of stent 500A adjacent outflow end 504 and skirt 800A isdisposed on the abluminal surface of the flared portion 450 of stent500A adjacent inflow end 502, as described above with reference to FIG.11. Additionally, three leaflets 1202 have been added to the interior ofstent 500A and attached to commissure features 508 and to selectedstruts of stent 500A and/or to cuff 600 to form a valve assembly asknown in the art. Engaging arms 518 may also extend toward inflow end502 and clip onto, or otherwise couple to, native valve leaflets to aidin anchoring stent 500A to the surrounding tissue. Though cuff 600covers many cells of stent 500A, engaging arms 518 remain unobstructedto adequately perform their function. When deployed at the mitral valveposition, prosthetic heart valve 1200 allows blood flow from atrium 122to left ventricle 124 and impedes blood backflow from left ventricle 124to left atrium 122. Flared portion 450 may be disposed at leastpartially within the native valve annulus and/or left atrium 122 toanchor prosthetic heart valve 1200 (e.g., reduce the possibility ofprosthetic heart valve 1200 migrating into left ventricle 124) and/orseal regions around prosthetic heart valve 1200 to reduce paravalvularleakage.

Several variations of the stent for a prosthetic heart valve arepossible. For example, FIG. 13 illustrates stent 1300 extendinggenerally between inflow end 1302 and outflow end 1304 and having threerows of cells 1310,1320,1330, similar to the cells of stent 500Adescribed above with reference to FIG. 5A. As shown, each row includesnine cells. The main difference between stent 500A and stent 1300 is theinclusion of horseshoes 1340,1342 to aid in suturing a cuff and a skirtto stent 1300. Specifically, corners C1 of cells 1322 closest to inflowend 1302 include first horseshoes 1340 to prevent slippage of sutureswhen coupling a cuff to stent 1300, and corners C2 of enlarged cells1332 closest to inflow end 1302 include second horseshoes 1342 toprevent slippage of sutures when coupling a skirt to stent 1300.

The shape of the engaging arms may also be modified in several ways. Inthe simplest configuration, shown in FIG. 14A, stent 1400A includes afirst row 1410A of cells 1412A. Each substantially diamond-shaped cell1412A is composed of four struts 1416 a-d joined to one another asshown, struts 1416 a and 1416 b forming an angle (31 therebetween.Nested engaging arms 1418A are formed of two substantially straightstruts 1419 that are coupled to struts 1416 c and 1416 d at first endsr1 and to each other at second ends r2. Because of the shape of cells1412A there is little room to form engaging arms 1418A, resulting in asharp tip at second ends r2 and a tight angle at first ends r1.

Instead of laser cutting a tube to create a stent in a collapsed state,the tube may be laser cut to create a stent in a partially expandedstate. Cutting a stent from a larger diameter tube provides a largerarea inside the cells of the stent to form engaging arms. Stent 1400B ofFIG. 14B has been formed using this method and generally includes firstrow of cells 1410B having first cells 1411B and second cells 1412B,second cells 1412B being formed of struts 1417 a-d. First cells 1411Bthat will not include engaging arms may be substantially diamond-shaped,while second cells 1412B that include engaging arms 1418B have a secondshape that does not form a diamond. Specifically, struts 1417 a and 1417b of cell 1412B may form a slight curvature such that the upper portionof cell 1412B is rounded and forms an angle β2, larger than angle β1,for receiving engaging arms 1418B. With the larger angle β2, an engagingarm 1418B may be formed with a curved loop 1419 having a smooth surfaceat position r2 that would be less traumatic if brought in contact withbody tissue. Additionally, curved loop 1419 includes a wider takeoff atposition r1 to reduce or eliminate a pinch point, resulting in less of astress concentration on the anatomy that is contacted by stent 1400B andeasier loading within a delivery device.

As described in the previous examples, engaging arms are not disposedwithin each cell of first row 1410B. Thus, in forming a stent havingengaging arms, the various features of stent 1400B may be cut from ametal tube under different conditions. For example, cells 1411B that donot have engaging arms 1418B may be cut when the tube is in a radiallycollapsed condition, and cells that include engaging arms 1418B may becut when the tube is in a partially expanded condition. This approachavoids the need for cutting stent 1400B out of a large diameter tube asthe large diameter tube can be expensive and more difficult tomanufacture. Selectively cutting portions in the collapsed and partiallyexpanded conditions allows for manufacturing the configurations shownout of a relatively small diameter tube.

In another variation shown in FIG. 15, stent 1500 may include featuresto aid in visualization during deployment. Stent 1500 may besubstantially similar to stent 500A described above, and may include afirst row 1510 of cells having first cells 1511 and second cells 1512,second cells 1512 including engaging arms 1518 therein. The maindifference between stent 1500 and stent 500A is the presence of abridging strut 1520 extending between the struts forming each engagingarm 1518 as shown. Bridging struts 1520 include a circular support 1525for accepting a radiopaque marker (e.g., tantalum markers) to help makeengaging arms 1518 more visible under fluoroscopy and/orechocardiography. Thus, the orientation of stent 1500 with respect tothe native valve annulus may be more accurately detected so thatengaging arms 1518 may be aligned with the native valve leaflets.

Additional variations in the configurations of the stents are possible.For example, the stent may optionally include a braided material in avariety of configurations. These braided portions may be combined invarious manners with any of the stents and cuffs previously described orwith variations of the engaging arms as will be discussed below. Thus,the teachings of the present disclosure are not independent and variousfeatures may be combined to achieve one or more benefits, such asreduced paravalvular leakage, better anchoring, a better crimp profileand the like.

For example, as previously described with reference to FIG. 3, aprosthetic heart valve may be formed with a frame of braided materialsurrounding the stent to reduce paravalvular leakage by engaging tissueand filling spaces between the prosthetic valve and the native valveannulus. In addition to what has been already described, the braidedmaterial may be disposed on the stent in various other configurations.Two such variations are shown in FIGS. 16A-D. Though the valve assemblyincluding the cuff and leaflets are not shown, it will be understoodthat any of the variations described above for forming the valveassembly may be combined with the stents and frames of FIGS. 16A-D.

As shown in FIG. 16A, a stent 1601 for a prosthetic heart valve has aninflow end 1602, an outflow end 1604 and a plurality of struts 1605forming one or more rows of cells 1610. Stent 1601 includes a number ofengaging arms 1618 similar to engaging arms 1518, each engaging armhaving a bridging strut 1620 and a circular eyelet 1625 formed by a loopin the bridging strut 1620. One noteworthy feature of this variation isthe use of a braided crown 1630 at inflow end 1602 of stent 1601. Inthis example, braided crown 1630 is formed of any of the mesh-likematerials or configurations described above with reference to FIG. 3,and extends generally perpendicular to the longitudinal axis y of stent1601, flaring radially outward a distance dl of between about 5 mm andabout 15 mm from struts 1605 of stent 1601 in the expanded condition.

As shown, stent 1601 includes a single full row of cells 1610, engagingarms 1618 being coupled to selected cells. Engaging arms 1618 are tiltedat an oblique angle to the longitudinal axis, a feature that will bedescribed in more detail below with reference to FIGS. 18A-B. Braidedcrown 1630 is attached to stent 1601 via a plurality of connectors 1635,the braided material being crimped together at each connector andcoupled to a strut of the stent. In the example shown, a singleconnector 1635 is disposed above each cell 1610 such that in a nine-cellstent nine connectors 1635 are provided. It will be understood that moreor less connectors 1635 may be provided. For example, connectors 1635may skip one or more cells. In at least some examples, braided materialis crimped over itself and joined to the stent via welding, adhesive orother suitable techniques, connector 1635 being optionally cylindricaland disposed over the braided material and a strut of the stent.

FIG. 16B is a schematic representation showing the general profile ofbraided crown 1630. Braided crown 1630 generally includes verticalportions 1641 coupled to stent 1601 at the connectors as discussed, ahorizontal portion 1643 disposed generally perpendicular to verticalportions 1641, and a transition curvature 1642 between the verticalportion and the horizontal portion. In use, stent 1601 may be at leastpartially disposed the within native valve annulus while braided crown1630 may be disposed within the left atrium, the flared horizontalportion 1643 providing anchoring for the prosthetic heart valve so thatthe valve is incapable of migrating into the left ventricle.

In another variation, shown in an expanded condition in FIG. 16C, astent 1651 for a prosthetic heart valve has an inflow end 1652, anoutflow end 1654 and a plurality of struts 1655 forming two rows ofgenerally diamond-shaped cells 1660, 1661. Specifically, a lower row ofcells 1660 is disposed adjacent outflow end 1654 and is joined to anupper row of cells 1661 disposed adjacent inflow end 1652, each cell1661 of the upper row being defined by two struts 1665 a,1665 b that areshared with the lower cells and two additional struts 1665 c,1665 d(FIG. 16D). The upper and lower struts in upper cells 1661 are coupledtogether at junctions 1667, which coincide with the peaks of the lowercells 1660. Stent 1651 also includes a number of engaging arms 1668similar to engaging arms 1618, each engaging arm having a bridging strut1670 and a circular eyelet 1675 formed by a loop in the bridging strut1670. In this example, braided crown 1680 is disposed adjacent inflowend 1652 of stent 1651, portions of the braided wires being attached tostent 1651 with connectors 1685 at junctions 1667 via any of the methodsdescribed above with respect to FIGS. 16A-B.

Braided crown 1680 extends initially from connectors 1685 toward inflowend 1652 then bends over itself toward outflow end 1654. The generalprofile of braided crown 1680 is shown in FIG. 16E. In use, stent 1651including most of lower cells 1660 may be disposed within the nativevalve annulus while upper cells 1661 may extend into the left atrium,braided crown 1680 also being disposed within the left atrium to provideanchoring for the prosthetic heart valve so that the valve is incapableof migrating into the left ventricle.

As briefly mentioned, the engaging arms may also be constructed inseveral ways to provide additional benefits. Two additional examples ofengaging arms will now be described, which may be used with any of thestent examples discussed above. In FIGS. 17A-G, one example of anengaging arm known as a teeter-totter arm is shown. As shown in FIG.17A, stent 1700 extends between inflow end 1702 and outflow end 1704 andincludes a braided crown 1705, similar to crown 1680 and a plurality ofengaging arms 1710.

A more detailed view of a single engaging arm 1710 is shown in FIG. 17B.Engaging arm 1710 is nested within cell 1712, which is generally formedby two upper struts 1713 a,1713 b and two lower struts 1713 c,1713 d.Although generally diamond-shaped cells are described, it will beunderstood that variations of the cell shape are contemplated and thatterms such as “apex” and “corner” used herein are not to be takennarrowly as forming an angle, but rather as a position where two strutsmeet. Thus, struts may meet one another at apices or corners that have acurvature.

Engaging arm 1710 includes two connecting portions 1715 joined to lowerstruts 1713 c,1713 d, respectively, at junctions 1714, and two generallyparallel, longitudinally-extending struts 1716, which are joinedtogether at rounded end 1718. Connecting portions 1715 space engagingarm 1710 from the struts forming cell 1712. Junctions 1714 may bedisposed along lower struts 1713 c,1713 d at a distance x1 from corners1717, at which lower struts 1713 c,1713 d are connected to upper struts1713 a,1713 b, respectively. In one example, distance x1 is closer tocorners 1717 than to the lower apex 1711 of the cell (e.g., betweenapproximately one-quarter and one-third of the length of lower struts1713 c,1713 d). Bridging strut 1719 forming central eyelet 1720 extendsbetween longitudinally-extending struts 1716 as described in earlierexamples.

As will be appreciated from the figures, the joining of engaging arm1710 to the lower struts 1713 c, 1713 d allows engaging arm 1710 to movein response to the movement of lower struts 1713 c,1713 d. Thissynchronous movement of the engaging arms 1710 and the lower struts isshown in FIGS. 17C-F. As shown in FIG. 17C, in a relaxed condition bothengaging arm 1710 and lower struts 1713 c,1713 d may be biased radiallyoutward with respect to a longitudinal direction w1 of the stent.Specifically, in the relaxed condition, engaging arm 1710 may be joinedto lower struts 1713 c,1713 d at a fixed angle a1 of between about 90degrees and about 170 degrees. In the relaxed condition shown in FIG.17C, engaging arm 1710 may form a second angle a2 of between about 5degrees and about 85 degrees with respect to the longitudinal directionw1 of the stent. Also in the relaxed condition, lower struts 1713 c,1713d may form a third angle a3 of between about 5 degrees and about 85degrees with the longitudinal direction w1 of the stent.

Applying a force fl on lower struts 1713 c,1713 d radially inward towardthe center of the device causes the struts to pivot at corners 1717.This pivoting of struts 1713 c,1713 d radially inward result in acommensurate movement of engaging arm 1710 radially outward (FIG. 17D).When lower struts 1713 c,1713 d are pressed until they are parallel withlongitudinal direction w1, angle a3 becomes zero, and angle a2 is thesum of angles a2 and a3 in the relaxed condition. In some examples,angle a1 may remain substantially the same as in the relaxedconfiguration. Releasing lower struts 1713 c, 1713 d causes them totravel radially outward to the relaxed condition shown in FIG. 17C andengaging arm 1710 to travel radially inward also to the relaxedcondition.

The synchronous movement of lower struts 1713 c,1713 d and engaging arm1710 may be useful during delivery of a prosthetic heart valve as shownin FIGS. 17E-G. In FIG. 17E, stent 1700 is in a loaded condition withindelivery sheath 1750, engaging arms 1710 and struts 1713 c,1713 d beingparallel with the longitudinal direction w1 of stent 1700. To releasethe device, delivery sheath 1750 is retracted in the direction of arrowb1 toward the outflow end of the stent (not shown), while stent 1700remains fixed or is urged forward. As shown in FIG. 17F, in apartially-released condition in which sheath 1750 uncovers, engagingarms 1710 (i.e., as the free end of the sheath approach junctions 1714),the exposed portion of each engaging arm 1710 deflects outwardly to anangle a2 of approximately 45 degrees, while the lower struts (not shown)are still constrained within delivery sheath 1750. This allows engagingarm 1710 to flare outwardly at a wide angle to capture the native valveleaflet in the enlarged cavity 1770 between engaging arm 1710 and therest of stent 1700. Once the native valve leaflet is positioned withincavity 1770, delivery sheath 1750 may be further retracted in directionb1 to a fully-released (e.g., relaxed) condition to liberate lowerstruts 1713 c,1713 d, causing both the lower struts and the engaging arm1710 to return to their relaxed condition, whereby angle a2 is reducedto approximately 30 degrees, grasping the native valve leaflet withincavity 1770.

Additionally, or in the alternative, the engaging arms may be heat-setso as to be inclined toward one another to aid in visualization duringdeployment. As shown in FIG. 18A, stent 1800 extends between inflow end1802 and outflow end 1804 and includes a braided crown 1805, similar tocrown 1680 discussed above, and one or more pairs of engaging arms 1810a,1810 b. Engaging arms 1810 a,1810 b are not fully nested within cells1812, but are heat-set to slope diagonally toward one another.

A more detailed view of a single engaging arm 1810 is shown in FIG. 18B.Engaging arm 1810 is connected to cell 1812, which is generally formedby two upper struts 1813 a,1813 b and two lower struts 1813 c,1813 d.Engaging arm 1810 includes two connecting portions 1815 joined to lowerstruts 1813 c,1813 d, respectively, at junctions 1814 and two generallyparallel, longitudinally-extending struts 1816, which are joinedtogether at rounded end 1818. Bridging strut 1819 forming central eyelet1820 extends between longitudinally-extending struts 1816. Engaging arm1810 may be heat-set so that, in the relaxed condition, engaging arm1810 slopes at an angle a4 of between about 5 degrees and about 80degrees with respect to a longitudinal axis w2 of cell 1812.

When disposed within a delivery sheath 1850, engaging arms 1810 a,1810 bmay at least partially overlap with one another during deployment (FIG.18C). In some examples, the extent of the overlap of engaging arms 1810a,1810 b may result in circular eyelets 1820 a,1820 b being directlyaligned with one another. In another example, the extent of the overlapof engaging arms 1810 a, 1810 b may result in an overlap of at least thetwo directly opposed longitudinal struts 1816 b of respective engagingarms. It will be understood that a stent may have several pairs ofengaging arms (e.g., two pairs of engaging arms or three pairs ofengaging arms) and that each engaging arm may crisscross with acomplementary engaging arm. As engaging arms 1810 are released, theytravel further apart until the stent takes the shape shown in FIG. 18A.

In some embodiments, a prosthetic heart valve has an inflow end, anoutflow end and a longitudinal axis extending from the inflow end to theoutflow end and includes a collapsible and expandable stent including aplurality of cells arranged in at least one row extending around acircumference of the stent. The stent further includes at least oneengaging arm joined to one of the cells adjacent the outflow end andhaving a free end extending toward the inflow end, the engaging armbeing movable between a loaded condition in which the engaging arm isoriented substantially parallel with the longitudinal axis of the stent,a partially-released condition in which the engaging arm forms a firstangle with the longitudinal axis of the stent, and a fully-releasedcondition in which the engaging arm forms a second angle with thelongitudinal axis of the stent, the first angle being larger than thesecond angle. A collapsible and expandable valve assembly is disposedwithin the stent and having a plurality of leaflets.

In some examples, the at least one engaging arms may include twoengaging arms for coupling to each native valve leaflet at a site ofimplantation; and/or the engaging arm may include twolongitudinally-extending struts coupled together at a rounded end;and/or the engaging arm further may include a bridging strutinterconnected between the two longitudinally-extending struts, thebridging strut including a loop defining an eyelet; and/or the engagingarm may be nested within the one cell, the one cell having two upperstruts joined to one another at an upper apex, two lower struts joinedone another at a lower apex, the lower struts being joined to the upperstruts at corners, the engaging arm being joined to the lower struts ofthe one cell; and/or a rotation of the lower struts may cause acomplementary rotation of the engaging arm; and/or the engaging arm maybe joined to the lower struts at locations along lengths of the lowerstruts, the locations being closer to the corners than to the lowerapex; and/or in the fully-released condition, the engaging arm may forman angle of between about 90 degrees and about 170 degrees with thelower struts; and/or in the fully-released condition, the lower strutsmay form an angle of between about 5 degrees and about 85 degrees withthe longitudinal axis of the stent; and/or the first angle may bebetween about 40 and about 50 degrees, and the second angle may bebetween about 30 and about 40 degrees; and/or the prosthetic heart valvemay be a mitral valve.

In some embodiments, a prosthetic heart valve has an inflow end and anoutflow end, and may include a collapsible and expandable stentincluding a plurality of cells arranged in at least one row extendingaround a circumference of the stent. The stent further includes at leastone engaging arm joined to one of the cells adjacent the outflow end andhaving a free end extending toward the inflow end, the engaging armbeing connected to a selected cell, the one cell having two upper strutsjoined to one another at an upper apex, two lower struts joined oneanother at a lower apex, the lower struts being joined to the upperstruts at corners, the engaging arm being joined to the lower struts ofthe one cell and movable between a loaded condition and a relaxedcondition, the engaging arm being sloped with respect to a longitudinalaxis of the one cell in the relaxed condition. A collapsible andexpandable valve assembly may be disposed within the stent and having aplurality of leaflets.

In some examples, the engaging arm may be heat-set to form an angle ofbetween about 5 degrees and about 85 degrees with respect to thelongitudinal axis of the selected cell; and/or the at least one engagingarm may include two complementary engaging arms for coupling to eachnative valve leaflet at a site of implantation, the complementaryengaging arms being sloped toward one another in the relaxed condition;and/or the at least one engaging arm may include two complementaryengaging arms for coupling to each native valve leaflet at a site ofimplantation, the complementary engaging arms being at least partiallyoverlapped with one another in the relaxed condition; and/or theprosthetic heart valve may be a mitral valve.

In some embodiments, a method of delivering a prosthetic heart valve mayinclude providing a collapsible and expandable valve assembly and acollapsible and expandable stent having an inflow end, an outflow end,and a longitudinal axis extending from the inflow end to the outflowend, the stent including a plurality of cells arranged in at least onerow, each row extending around a circumference of the stent, the stentfurther including at least one engaging arm joined to one of the cellsadjacent the outflow end and having a free end extending toward theinflow end, the one cell having two upper struts joined to one anotherat an upper apex, two lower struts joined one another at a lower apex,the lower struts being joined to the upper struts at corners, theengaging arm being joined to the lower struts of the one cell. The stentand valve assembly may be loaded within a delivery sheath, and thedelivery sheath may be advanced to a patient's native valve annulus.

In some examples, the delivery sheath may be retraced a first distanceaway from the inflow end of the stent to release the engaging arm sothat the engaging arm forms a first angle with respect to thelongitudinal axis of the stent; and/or the delivery sheath may beretracted an additional distance away from the inflow end of the stentto release the lower struts so that the at engaging arm forms a secondangle with respect to the longitudinal axis of the stent, the secondangle being less than the first angle; and/or the method may include thestep of releasing the delivery sheath from the stent and removing thedelivery sheath from the body.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A prosthetic heart valve having an inflow end, an outflow end and alongitudinal axis extending from the inflow end to the outflow end,comprising: a collapsible and expandable stent including a plurality ofcells arranged in at least one row extending around a circumference ofthe stent, the stent further including at least one engaging arm joinedto one of the cells adjacent the outflow end and having a free endextending toward the inflow end, the engaging arm being movable betweena loaded condition in which the engaging arm is oriented substantiallyparallel with the longitudinal axis of the stent, a partially-releasedcondition in which the engaging arm forms a first angle with thelongitudinal axis of the stent, and a fully-released condition in whichthe engaging arm forms a second angle with the longitudinal axis of thestent, the first angle being larger than the second angle, the one cellhaving two upper struts joined to one another at an upper apex, twolower struts joined one another at a lower apex, the lower struts beingjoined to the upper struts at corners, the engaging arm being joined tothe lower struts of the one cell and movable between a loaded conditionand a relaxed condition, the engaging arm being sloped with respect to alongitudinal axis of the one cell in the relaxed condition; acollapsible and expandable valve assembly disposed within the stent andhaving a plurality of leaflets.